Limitation of the amount of chemical components in a detergent composition may limit the cost and make the composition more environmentally friendly. Accordingly, it is a constant duty for the fabricant of detergent compositions to reduce the quantity of chemical components in his compositions while still satisfying several criteria for the composition to be effective, such as cleaning and whiteness performance.
However, the benefits of limiting the chemistry are reduced if the consumer uses more product than required. This may especially happen if the consumer is not aware of the new product properties or if he relies on indirect factors, such as the presence of suds, to dose the product. The presence of suds in a washing or laundering operation has long been used by the consumer as a signal that the detergent is effective.
The need exists for a detergent composition which provides effective cleaning with reduced chemistry, which provides suds-formation, and which maintains suds volume and suds retention. It is an object of the present invention to provide a detergent composition with reduced chemistry which maintains a high level of suds as long as the composition is effective for its purpose. The present inventors have surprisingly found that pyrophosphates have a better capacity to promote suds-forming, suds volume, and/or suds duration than other phosphate builders such as tripolyphosphate.
Phosphate builders have been used in detergent compositions for many years. However, the use of pyrophosphate has been generally considered disadvantageous compared to other phosphate builders and therefore limited. Conventional formulations built with pyrophosphate exhibit a reduction in builder effectiveness as the level of pyrophosphate in the wash water decreases relative to the water hardness level, i.e. when the product is used at close to underbuilt conditions. This reduction in builder effectiveness is called the “pyro dip”. The pyro dip represents those molar ratios of builder capacity to hardness (B:H ratio) approaching and below 1:1 (compared to an overbuilt condition where the molar ratio of builder to hardness is greater than 1:1) where the pyrophosphate complex is insoluble and precipitates. The effect of the pyro dip in the washing process is an increase in soil redeposition on the clothes. Accordingly, preferred phosphate builders in detergent compositions are usually selected from other phosphates, such as tripolyphosphate, rather than pyrophosphate.
In the presence of moisture, linear polyphosphates can be hydrolysed to lower phosphate including orthophosphate and pyrophosphate. This reaction is called the reversion reaction. This hydrolysis can be accelerated at higher temperature (generally above 39° C.), and at extreme acidic or alkali conditions of pH, for example pH below 4 or 5 or above 9 or 10. Until now, when a composition comprising tripolyphosphate undergoes detergent processing, for example in a spray drying step, the amount of pyrophosphate in the composition is monitored to ensure that it is kept at an acceptably low level.
In one embodiment of the invention the pyrophosphate may be made in situ in the detergent making step by selection of temperature and/or air flow and/or other chemical constituents and/or pH and/or moisture conditions to increase reversion.
The inventors have now surprisingly found that a higher proportion of pyrophosphate can be acceptable and even desirable as they have found that pyrophosphate has a better capacity than tripolyphosphate to promote suds formation and increase suds volume and duration while not impairing the whiteness of the fabric when used in the compositions of the invention.